Butterflies Migrating South For The Winter Is One Of The Greatest Natural Events On Earth To Witness

Oct 01, 2018

Much like birds migrate to warmer locales for the winter, each Autumn, monarch butterflies begin a long journey from their Summertime breeding areas in the North Eastern United States and Canada to warmer overwintering areas in Southwestern Mexico.

Quite unlike birds, these butterflies embark on a one-way journey. Yes, I know what you are thinking:

What?! Why is it a one-way journey? Does something happen along the way? What prevents the Monarch Butterflies from making a round trip? And how do they know where to migrate, anyway?

To answer these questions we must first think about the nature of Monarch butterfly migration.

As summer creeps into autumn, the amount of sunlight per day decreases along with the temperature. The monarch butterflies, sensing this change abandon their feeding and and breeding practices in these colder locations and take off in search of a place that is warm enough and safe enough to relocate for the winter. This process of waiting out or living during the colder months is called Overwintering.

The area the monarchs settle is found high in the mountain ranges of Central Mexico and is typically referred to as their overwintering site or overwintering ground. Once they are in this location, millions of monarch butterflies nestle together on the branches Oyamel fir trees.

Often called sacred firs, the trees act as microclimatic structures that keep the butterflies safe. The tree canopy and ecosystem works as a barrier for the monarch butterflies. It regulates temperatures enough that it never gets too hot or too cold.

When the winter is over, the butterflies do partially make their way back north. Instead of going the entire way back they stop short in warmer climates in places like Texas, where they begin the process of mating and reproduction by laying eggs on milkweed plants.

In a matter of days, the incubation period ends with the hatching of beautifully colored gold, black, and white larvae. The monarch caterpillars eat much of the milkweed before forming a chrysalis, during the pupa stage, and becoming full-grown butterflies.

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